Why do I often have blue feet?

I am a teen, I often wondered why kids or teens mess with there feet when they are barefoot?

• My sister who is 12 does it and I wondered what the reason is, is it some habit that kids and teens do or something. My friend who is 13 does it also, when im at his house he grabs his barefoot and fiddles with his toes. Thanks for your input btw im 13 and I havnt done it but im curious as to why others do it, seems like a weird habit or something. Btw my sister and my friend do this when they are at home, relaxing by the tv, sitting in a chair or just laying around.

• Answer:

  I have no idea, I often find myself cracking my ankles or toes while watching TV. it may just be a habit lol